/Engine/Plugins/Experimental/TetMeshing/Source/TetMeshing/Public/Generate/TetMeshGenerator.h
Set the various internal buffers to the correct sizes for the given element counts
void SetBufferSizes ( int32 NumVertices, int32 NumTetrahedra, bool bIncludeTetIDs, int32 NumTriangles, bool bIncludeTriangleIDs )